An active-matrix liquid-crystal multi-color display panel structure has a matrix of color display pixels which are arranged in rows and columns and which have semiconductor switching devices respectively incorporated therein. Such semiconductor switching devices are typically thin-film transistors of, for example, the amorphous-silicon field-effect design. Development of such multi-color display panel structures have significantly increased the display capacities of liquid-crystal display devices in general and provides ease of using multi-color display capabilities of liquid crystals.
One of the methods of producing multi-color images on liquid-crystal display panels is to use a dichroic pigment dissolved as a guest in a host liquid crystal. Another method is to use color filters provided in association with pixel electrodes across a layer of liquid crystal. The latter method is presently more frequently used than the former because of the extreme difficulties encountered in producing images of multiple colors by the guest-host method.
As well known in the art, a liquid-crystal multi-color display panel structure using color filters comprises two transparent substrates having a layer of liquid crystal sandwiched therebetween. A common electrode defining a display area of the panel structure is attached to one of these transparent substrates and an array of color filters selectively assigned to, typically, three primary colors of red, green and blue is disposed on this substrate. On the other of the two transparent substrates is formed a multiplicity of color display pixels arranged in rows and columns in such a manner as to be in registry with the individual color filters, respectively. Each of the color display pixels is composed of a pixel electrode and a switching device which is typically implemented by a thin-film field-effect transistor. The pixel electrode of each color display pixel is capacitively coupled with the common electrode across the layer of liquid crystal provided between the two substrates. The thin-film field-effect transistor implementing the switching device of each pixel has its gate connected to a row or scanning line of the pixel array and its current path connected between the pixel electrode and a column or signal line of the pixel array.
When the switching device forming part of a particular pixel is actuated to turn on with a scanning signal applied through the row line to the gate of the transistor, the liquid crystal intervening between the common electrode and the pixel electrode of the pixel is activated to allow passage of light therethrough. Light having an appropriate wavelength selected for the color filter associated with the particular color display pixel is thus passed through the color filter so that a picture element in any of a total of eight different colors can be produced by a triad of pixels respectively assigned to the three primary colors. If the field generated in the liquid crystal is varied continuously by controlling the voltage to be applied to each of the pixel electrodes, a full-color picture can be produced which is composed of picture elements with steplessly varied color tones.
In a known liquid-crystal multi-color display panel structure of the type using color filters, image display pixels individually assigned to the three primary colors recur in each of the rows or in each of the columns of the pixel array. A display panel structure having such pixel arrangement has a drawback in that there may be a case where one and the same color is assigned to all the pixels of a column or all the pixels of a row. In this instance, picture elements of identical colors appear throughout a column or a row of the resultant picture and thus produce a "stripe" extending vertically or horizontally of the picture displayed.
Research and development efforts have therefore been made to eliminate such stripes produced in pictures produced by such a known liquid-crystal multi-color display panel structure. These research and development efforts have resulted in, for example, a liquid-crystal multi-color display panel structure disclosed in Japanese Provisional Patent Publication No. 59-61818. A multi-color display panel structure therein taught uses a pixel pattern which is arranged such that each of the picture elements of each row is to be displaced or offset by one-third of the width of each picture element from each of the picture elements of each of the adjacent rows.
In this advanced multi-color display panel structure, the pixels forming each column are assigned to primary colors which appear recurrently in the direction of column so that an identical pixel pattern appears for every adjacent three of the rows of pixels. In other words, a combination of adjacent three rows of pixels forms one pixel pattern and a combination of adjacent three rows of pixels including two of the three rows of the former combination forms another pixel pattern.
A prior-art multi-color display panel structure of this nature however has a drawback in that one and the same color appears successively in a diagonal direction of the picture produced by the panel structure. The picture elements of the identical colors thus appearing diagonally of the picture produce colored moires in the resultant multi-colored display. Colored moire images are produced not only by the series of diagonally disposed, single color picture elements but by the series of intermediate or mixed color picture elements produced by pairs of pixels paired in each row and disposed diagonally of the picture area.
There has been proposed another type of multi-color display panel structure in which image display pixels are arranged to form generally triangular triads each bridging two rows, or columns, of the array. The individual image display pixels forming each triads are assigned to three different primary colors, respectively, and are alternately inverted in the directions of columns, or rows, in and along each pair of adjacent rows, or columns. This arrangement of image display pixels is useful in that the triangular triads of the pixels produce picture elements which are more like "dots" than the picture elements produced by triads each composed of pixels disposed in a single row or in a single column.
A prior-art multi-color display panel structure of this nature however has a drawback in that two rows of pixels must be scanned concurrently to activate a triad of pixels to produce a single picture element and, for this purpose, the color signals to be supplied to the column or signal lines of the pixel array must be re-formulated for the row or scanning lines connected to the particular two rows of pixels. This results in added complexity of the control circuit for the pixel array.
It is, accordingly, an important object of the present invention to provide an improved active-matrix liquid-crystal multi-color display panel structure which will produce neither stripes nor moire-images in the multi-color display using color filters.
It is another important object of the present invention to provide an improved active-matrix liquid-crystal multi-color display panel structure which is capable of achieving far higher resolution of picture elements than in prior-art multi-color display panels.
It is still another important object of the present invention to provide an improved active-matrix liquid-crystal multi-color display panel structure which will allow the use of a simple control circuit for the control of the color signals to be supplied to the column or signal lines of the pixel array.
It is still another important object of the present invention to provide an improved active-matrix liquid-crystal multi-color display panel structure having color display pixels which are more square-shaped than those used in prior-art multi-color display panels and will thus provide ease of fabrication of the active-matrix and common electrode substrates of the panel structure.